The Gatsby Migration, pt.1 - Setting the Scene

21 January 2020

Updated: 03 September 2023

Introduction

Lately I’ve been a little concerned with my current SPA approach on my personal site as well as a few others. More specifically the high initial load time due to the calls to the backend to retrieve content

With the aim of solving this problem I’ve spent a lot of time looking at and playing with Static Site Generators.Foreword: they’re all a lot more complicated than one would think

So for a static site the “static” content only changes so often, based on this we can generate page content with the data we’re planning to load in - that’s what we’re going to try to do

Now we’ll be starting off with a React app generated with create-react-app so that we can have a starting point for our Gatsby site as well as understanding how we can approach some of the challenges when switching over to a site generator like Gatsby

For the sake of completeness, this series will be broken into four posts covering the following:

  1. Creating the initial React App (This post)
  2. Rendering the “Dumb” pages with Gatsby
  3. Rendering the “Smart” page with Gatsby

The React App

First we’re going to be starting off with a new React app that we will work on changing into a Gatsby one parts 2 and 3, we’ll then focus on using plugins to enhance our content in 4

For this part we’ll build a basic React app that has the following:

  1. Two “hard-coded” pages and a 404 page
  2. A dynamic page with an API call to retrieve data
  3. Overall app layout with child routes for 1 - 3

To get started, we’ll create a fresh React App:

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npx create-react-app gatsby-to-be

And add the react-router

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yarn add react-router-dom

Running this command should set up the application, if you don’t know much about React I’d suggest taking a look at the documentation

Next cd gatsby-to-be and run yarn start, you should be able to visit the application in your browser at http://localhost:3000/

Looking at the generated files we have a public directory with some icons, an index.html file into which our React application will run once built, and a src directory that has the application code. The index.js file is what loads the application into the DOM and the App.js file which is the main component for our application

Hard Coded Pages

We will create the following three hard-coded pages in the src/pages directory

These pages are just React components that we will assign Routes to.

The pages we are using are known as functional components because they are javascript functions that return JSX

If we intend to use JSX in a file we need to ensure that we import React. The other component we are importing is the Link component which is a lot like a normal HTML a tag but with some special functionality to make the client-side navigation work

Blog.js

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import React from 'react'
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import { Link } from 'react-router-dom'
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const Blog = () => (
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  <div className="Blog">
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    <h1>Blog</h1>
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    <p>This is the Blog page</p>
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    <div>
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      <Link to="/blog/post-1">Post 1</Link>
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    </div>
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    <div>
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      <Link to="/blog/post-2">Post 2</Link>
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    </div>
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  </div>
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)
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export default Blog

Additionally we have the Home.js and NotFound.js files which are similar to the Blog.js file we created

Home

Home.js

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import React from 'react'
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const Home = () => (
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  <div className="Home">
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    <h1>Home</h1>
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    <p>This is the Home page</p>
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  </div>
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)
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export default Home
Not Found

NotFound.js

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import React from 'react'
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const NotFound = () => (
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  <div className="NotFound">
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    <h1>404</h1>
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    <p>Page Not Found</p>
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  </div>
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)
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export default NotFound

Dynamic Post Page

Next up we’ll create a component that can render out content for a blog post. This will consist of a few hooks which are react functions that we can use to sort of control the data in a function

The Post component will:

  1. Display a loading indicator initially
  2. Figure out what post we’re trying to render based on the URL
  3. Retrieve a JSON file from the public directory based
  4. Set the component state after reading the file
  5. Display the content from the file in a JSX template

The useState hook is used to initialize the state the component, in this case using the hasError and data variables, as well as providing the functions necessary for updating those in the form of setHasError and setData respectively

We use fetch in the useEffect hook to retrieve the data from the public directory. The useEffect hook allows us to pass a function that will be called to update side effects. The second input, in our case [] is the array of objects that, when are changed, we want the hook to run - since we only want it to run once and don’t care about any other state changes we pass in an empty array for this value

Post.js

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import React, { useEffect, useState } from 'react'
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const Post = ({ match }) => {
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  const slug = match.params.slug
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  const [hasError, setHasError] = useState(false)
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  const [data, setData] = useState(null)
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  useEffect(() => {
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    const fetchData = async () => {
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      try {
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        const res = await fetch(`/posts/${slug}.json`)
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        const json = await res.json()
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        setData(json)
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      } catch (error) {
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        console.log(error.toString())
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        setHasError(true)
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      }
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    }
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    fetchData()
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  }, [])
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  return (
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    <div className="Post">
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      <p>
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        This is the <code>{slug}</code> page
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      </p>
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      {data ? (
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        <div className="content">
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          <h1>{data.title}</h1>
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          <p>{data.body}</p>
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          <img src={data.image} alt="" />
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        </div>
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      ) : hasError ? (
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        <div className="error">
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          <h1>Error</h1>
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          <p>{hasError}</p>
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        </div>
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      ) : (
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        <p>Loading .. </p>
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      )}
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    </div>
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  )
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}
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export default Post

In the above component we’re making use of the following pattern to decide what to render conditionally:

  1. If the data is loaded then show the data
  2. Else if there is an error then show the error data
  3. Otherwise show a loading message

The way we are rendering the Post component with a parameter for match. The match parameter will be passed in as a prop from the Router that we will configure next, this allows us to use the slug from the URL to retrieve the content for the page

The two data files we have to pull content from in the public/posts directory are post-1.json and post-2.json

Post 1 - JSON

post-1.json

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{
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  "title": "Post 1",
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  "body": "Hello world, how are you",
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  "image": "/posts/1.jpg"
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}
Post 2 - JSON

post-2.json

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{
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  "title": "Post 2",
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  "body": "Hello world, I am fine",
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  "image": "/posts/2.jpg"
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}

The images posts/1.jpg and posts/2.jpg can also just be any images in that directory

App Layout and Routes

Lastly, we’ll specify our application layout with the relevant routes in the App.js file, referencing the components we have created, we do this using the BrowserRouter. When we switch the project over to a Gatsby one, the App.js file will be converted into our Layout component to wrap our different pages

We use the Router component and the page inside of it, this essentially handles Routing via the Link components. Next we have a div as a wrapper for our component as well as a header, nav, and main tags to organise the page

The Route component takes in the component that we would like to display for a given route, and the Switch helps us to ensure that only route is actively being fisplayed at a time. The Switch will navigate from the first to last Route and render the first one that matches the given path

Fow now, our App.js file is as follows:

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import React from 'react'
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import './App.css'
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import { BrowserRouter as Router, Link, Switch, Route } from 'react-router-dom'
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import Home from './pages/Home'
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import Blog from './pages/Blog'
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import Post from './pages/Post'
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import NotFound from './pages/NotFound'
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const App = () => (
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  <Router>
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    <div className="App">
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      <header>
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        <nav>
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          <h1>My Website Title</h1>
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          <Link to="/">Home</Link>
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          <Link to="/blog">Blog</Link>
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        </nav>
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      </header>
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      <main>
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        <Switch>
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          <Route exact path="/" component={Home}></Route>
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          <Route exact path="/blog" component={Blog}></Route>
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          <Route exact path="/blog/:slug" component={Post}></Route>
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          <Route path="/*" component={NotFound}></Route>
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        </Switch>
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      </main>
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    </div>
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  </Router>
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)
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export default App

In the above component we can see that where we are rendering the Post component we have a parameter in the route called slug, this parameter will be passed in to the Post component as part of the match object

Summary

We have built a fairly simple application that makes use of both static and data-based pages, we have also tied all of these together using the App component and a Router with the following routes:

  1. / which will render the Home component
  2. /blog which will render the Blog component
  3. /blog/:slug which will render the Post component and retrieve the data based on the given slug
  4. /* which will match any other routes and render the NotFound component

In the next post we’re going to look at how to take what we have so far and transform this application into a Gatsby one, but for now it may be useful to think about what kind of steps we may need to take if we’d like to make this a static website based on the way our current routes work

Nabeel Valley